Do Magistrate Judges Have a Power to Refuse To Sign Warrants Based on Expectations of How a Warrant Would be Executed?:
The Ninth Circuit's new computer search and seizure decision is particularly interesting because of the way it empowers magistrate judges. It envisions magistrate judges as activity overseeing the computer search warrant process, and in particular having the power and duty not to sign warrants unless the judge is satisfied that the warrant will be executed in a way that sufficient protects privacy. The opinion goes out of its way to task magistrates with the job of doing what they need to do to protect privacy:
[W]e must rely on the good sense and vigilance of our magistrate judges, who are in the front line of preserving the constitutional freedoms of our citizens while assisting the government in its legitimate efforts to prosecute criminal activity. Nothing we could say would substitute for the sound judgment that judicial officers must exercise in striking this delicate balance.
  Among the new powers that the Ninth Circuit today specifically bestowed on magistrate judges is this one:
The government should, in future warrant applications, forswear reliance on the plain view doctrine or any similar doctrine that would allow it to retain data to which it has gained access only because it was required to segregate seizable from non-seizable data. If the government doesn’t consent to such a waiver, the magistrate judge should order that the seizable and non-seizable data be separated by an independent third party under the supervision of the court, or deny the warrant altogether.
(emphasis added). This raises a very important question that the Ninth Circuit doesn't address, perhaps because it never occurred to the judges on the en banc court: Does a magistrate judge have the power to refuse to sign a warrant that is based on probable cause and is constitutionality particular but that the magistrate judge fears would be executed in a way that is unconstitutional or otherwise too invasive?

  The precedents I am aware of suggest that the answer is "no." See Abraham S. Goldstein, The Search Warrant, the Magistrate, and Judicial Review, 62 N.Y.U. L. Rev. 1173, 1196 (1987) ("The few cases on [whether a magistrate judge can refuse to issue a warrant on the ground that the search may be executed unconstitutionally] hold that a judge has a 'ministerial' duty to issue a warrant after 'probable cause' has been established."); In re Worksite Inspection of Quality Products, Inc., 592 F.2d 611, 613 (1st Cir. 1979) (noting the limited role of magistrate judges in issuing search warrants); Ex Parte United States, 287 U.S. 241, 250 (1932) (holding that a magistrate judge did not have discretion to refuse to issue an arrest warrant after the the grand jury returned an indictment, and noting that "the refusal of the trial court to issue a warrant . . . is, in reality and effect, a refusal to permit the case to come to a hearing upon either questions of law or fact, and falls little short of a refusal to permit the enforcement of the law.").

  I think these authorities make a lot of sense. Under the Fourth Amendment, the magistrate's job is to determine if the warrant is based on probable cause and is sufficiently particular. These are the only requirements of the facial validity of a warrant, and so I would think are the only grounds for a magistrate judge denying a warrant. Otherwise you end up with a tricky situation. Imagine a magistrate refuses to sign a warrant unless the government makes promises as to how the warrant will be executed. On one hand, if the government's promises are enforceable, then the magistrate judge gets to determine the Fourth Amendment as she pleases regardless of what the district judges, circuit judges, and Supreme Court Justices say the law actually is. On the other hand, if the promises the government makes are unenforceable, then you end up with the very awkward situation of the government making a promise to a federal judge and then feeling free to break it.

  Neither of these options are very good ones. But in my view neither is necessary, either: I don't think magistrate judges have the power to condition signing warrants on grounds other than probable cause and particularity. The constitutionality of how the warrant is executed is a question for judicial review after the warrant is executed, not negotiations with a magistrate beforehand. At least that's the traditional understanding: It appears to be no longer the law in the Ninth Circuit as of this morning.